U.S. President Donald Trump’s former lawyer, Michael Cohen, was in touch as far back as 2015 with a Russian who offered “political synergy” with the Trump election campaign, the federal special counsel said Friday in a court filing.

Filings by prosecutors from both New York and the Trump-Russia special counsel’s office laid out for the first time details of the co-operation of Cohen, a vital witness who once said he’d “take a bullet” for the president but who in recent months has become a prime antagonist and pledged to come clean with the government.

Federal prosecutors said Friday that Cohen deserves a substantial prison sentence despite his co-operation with investigators. He is to be sentenced next week, and may face several years in prison.

In hours of meetings with prosecutors, Cohen detailed his intimate involvement in an array of episodes, including some that directly touch the president, that are at the centre of investigations into campaign finance violations and potential collusion between the Trump campaign and the Kremlin.

In one of the filings, Mueller details how Cohen spoke to a Russian who “claimed to be a ‘trusted person’ in the Russian Federation who could offer the campaign ‘political synergy’ and ‘synergy on a government level.’”

Cohen also discussed a Moscow real estate deal that could have netted Trump’s business hundreds of millions of dollars and conversations with a Russian intermediary who proposed a meeting between Trump and Russian President Vladimir Putin as well as offering synergy with the campaign, prosecutors said.

Cohen, dubbed Trump’s “legal fixer” in the past, also described his work in conjunction with Trump in orchestrating hush money payments to two women — a porn star and a Playboy model — who said they had sex with Trump a decade earlier. Prosecutors in New York, where Cohen pleaded guilty in August in connection with those payments, said the lawyer “acted in co-ordination and at the direction” of Trump.

Despite such specific allegations of Trump’s actions, the president quickly tweeted after news of the filings: “Totally clears the President. Thank you!”

In addition, the filings reveal that Cohen told prosecutors he and Trump discussed a potential meeting with Putin on the sidelines of the U.N. General Assembly in 2015, shortly after Trump announced his candidacy for president.

In a footnote, special counsel Robert Mueller’s team writes that Cohen conferred with Trump “about contacting the Russia government before reaching out to gauge Russia’s interest in such a meeting,” though it never took place.

In an additional filing Friday evening, prosecutors said former Trump campaign chairman Paul Manafort lied to them about his contacts with a Russian associate and Trump administration officials.

Manafort, who has pleaded guilty to several counts, violated his plea agreement by then telling “multiple discernible lies” to prosecutors, they said.